In automotive air conditioning systems it is desirable to control the evaporator pressure (temperature) to prevent freezing condensed moisture on the evaporator which blocks air flow. The present controls for this purpose are complex and subject to malfunction if contaminated by dirt or moisture entrained in the refrigerant. The present controls do not fail safe. Thus failure may lead to failure of other system components. The temperature change in refrigerant flowing through the valve in flooded systems can increase the evaporator pressure differential depending upon the cooling load.